1. Field of the Invention
The present invention relates to a semiconductor device, more particularly, to a wire bonding method for producing the device.
2. Description of the Prior Art
A semiconductor device comprises a ceramic package and a semiconductor chip housed within the package. Electrode pads formed on the semiconductor chip and electrode pads formed on the package are connected with wires by the wire bonding apparatus. The semiconductor chip and the vessel or package become larger, and the number of electrodes are increased. Therefore, the number of wires for bonding the electrodes of the semiconductor chip and the electrodes of the package also increases. For example, two hundred wires are required for bonding the electrodes of an LSI.
In a conventional wire bonding method, first an end of a wire is bonded to an electrode pad of the semiconductor chip by scrubbing the bonding wedge of the wire bonding apparatus. Then the wire is pulled upward and moved toward an electrode pad of the package. The wire is then obliquely moved downward onto the electrode pad of the package and bonded thereto by scrubbing the bonding wedge. The wire is but at the outside of the bonding portion so that the electrode pad of the semiconductor chip and the electrode pad of the package are bonded together by the wire.
In the conventional wire bonding method using the wire bonding apparatus (described later), the interval between two adjacent wires must be large enough to allow the vertical movement of the wire bonding apparatus at the rising portion of the wire above the electrode pad of the semiconductor chip, so as to avoid contact between the clamper behind the bonding wedge and the wires. Thus, a close arrangement of the wires cannot be achieved, which impedes the realization of a compact semiconductor device. Also, the electrode pad of the package must be large enough to avoid the abutment of the clamper of the wire bonding apparatus against the rear wall behind the electrode pad of the package. This also impedes the realization of a compact and small-sized semiconductor device.
In addition, in the above-mentioned wire bonding method, the wires are apt to accidentally come into contact with each other when the number of wires is increased, since the wires are disposed in a loop-shape above the electrode pads.